1.2: Which files do I actually need to play?
From the original game, you will need a valid (i.e. unmodified) version of the file "duke3d.grp" from Duke3D v1.3d or v1.5 Atomic CD. Shareware group can also be used. Any other file may be ignored.
You will then need an OpenGL port. Usually, the HRP releases contain EDuke32. For latest versions of the binaries, you should visit the EDuke32 site (see "Links" section).
The HRP itself is highly recommended, but not (!) necessarily needed if you don't want highres content (e.g. if you are playing on a slower machine or in case you are curious to see what the game originally looked like). In order to be fully up-to-date, look for both the latest "HRP Update Pack" and "Maphacks Reloaded". Load them with additional /g parameters after the HRP, e.g. E:\Duke3D\eduke32.exe /gduke3d_hrp.zip /ghrp_update.zip /gmaphacks.zip

1.3: What do I do with the Update Pack file?
You have two options: You can either put everything that's in the HRP Update Pack zipfile into the official HRP file. You will need a compression tool like WinRAR or WinZip for that. Decompress Update Pack contents to your hard drive, then open HRP zipfile and add all decompressed contents (no compression rate, i.e. "store files", is recommended). Make sure folder structure is maintained!
The other method is simpler, yet it requires you to use the HRP Update Pack as an additional startup parameter: Load the pack *after* the old HRP file, e.g. E:\Duke3D\eduke32.exe /gduke3d_hrp.zip /ghrp_update.zip. While your startup command line gets longer that way, you won't have to edit your original HRP zipfile, which can be useful if you want to keep it as a backup.

1.4: What are these maphacks? How do they work, and why do I need them?
Try starting EDuke32 or JFDuke3D without using them once and you will pretty soon see for yourself why they are necessary. :) In original Duke3D, 2D sprites were used, meaning these flat bitmaps were always facing towards the player and therefore always into the right direction. With the 3D models being used now, this has changed. Models have predefined viewing angles, and if the sprites in the game haven't been placed 100% correctly (which was not required in the first place), the models will be aligned badly. This means a shotgun pickup could clip into a wall, items like keycards facing away from you and so on. With maphacks, you can "rotate" these models around their center axis manually so that they face the player (again) and can be viewed from the best angle possible.
These hacks can either be put into the root dir of the HRP (which will cause them to be loaded on startup automatically) or used as a separate startup parameter after the HRP, e.g. E:\Duke3D\eduke32.exe /gduke3d_hrp.zip /gmaphacks.zip.

1.5: Are the update packs cumulative or consecutive?
The question is whether a newly released update pack contains everything that has been published in earlier updates or you need the last available file and put the new stuff in there. The simple answer is: Download a new update pack, and you can forget anything that has been released before.

1.6: Please tell me how to add parameters!
- Create a shortcut to "eduke32.exe" on your desktop (right-click on file in Windows Explorer -> "Send to" -> "Desktop").
- Right-click on EDuke32 icon, select "Properties".
- In the tab "Shortcut", add any parameter you wish behind "eduke32.exe". Syntax is: /gFilename (no spaces between parameter and filename!)
- Don't forget to leave 1 blank between each parameter, e.g.: E:\Duke3D\eduke32.exe /gFile1.zip /gFile2.zip
- Press "Apply"/"OK" and you are done. Start game with your modified shortcut.

1.7: What is the "autoload" feature?
The autoload feature is a function available in newer EDuke32 snapshots: Create a directory named "autoload" in your EDuke32 directory. Any .grp or .zip file you put in there will be loaded automatically, i.e. you don't have to use any parameters, just execute eduke32.exe. This is a great way to start the HRP with Update Pack for beginners who don't have any idea how to use parameters in shortcuts.
Note, however, that the loading sequence is still important. In the autoload dir, all files are loaded alphabetically, so you must make sure HRP (duke3d_hrp.zip) comes first, the Update Pack (hrp_update.zip) second and the optional SD_Duke mod (sd_duke.zip) third. If you leave all file names unaltered, it should work just fine.
You can still use parameters (see 1.6) to override the alphabetical loading sequence in the autodir folder.

1.8: I have installed a new graphics card (or updated drivers etc.), and now I am getting messed-up graphics. What's wrong?
If this happens, you are using EDuke32 with texture caching enabled (which is recommended). You have played the game before and it has created a "texcache" subdir with various cache files in it. These contain data for your old card, but *NOT* your new one which is not detected automatically by the game/port.
All you have to do is delete the "texcache" dir and let EDuke32 recreate it with new cache files the next time you fire up the game.